Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and non-volatile (e.g., flash) memory.
Flash memory devices typically use a one-transistor memory cell that may allow for high memory densities, high reliability, and low power consumption. Changes in threshold voltage of the memory cells, through programming of a charge storage structure such as floating gates, trapping layers or other physical phenomena, may determine the data state of each cell.
The memory cells may be arranged in strings of memory cells where each string may be coupled to a source. Groups of strings of memory cells (e.g., memory blocks) may all be coupled to a common source.
When a memory manufacturer desires to increase a memory density of a memory device, additional groups of strings of memory cells may be added to the memory device and coupled to the common source. Thus, the common source may be increased in length, thereby increasing its resistance.
It may be desirable to keep the resistance of the source as low as possible since, as is known in the art, a larger resistance may cause a larger voltage drop from a particular point of the circuit to the common source. A larger voltage drop can cause problems during memory operations that rely on very small voltage differences.